WASHINGTON (CNN) -- For the second time in three days, Sen. Hillary Clinton told reporters that the pledged delegates awarded based on vote totals in their state are not bound to abide by election results.

Sen. Hillary Clinton lags behind Sen. Barack Obama in the popular vote and in pledged delegates.

It's an idea that has been floated by her or a campaign surrogate nearly half a dozen times this month.

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The last time a major candidate lobbied pledged delegates to switch sides was at the 1980 convention, when Ted Kennedy's campaign tried to recruit delegates who arrived at the convention supporting eventual nominee Jimmy Carter.

After that battle, the Democratic Party altered a provision that required pledged delegates to support the candidate they had arrived at the convention to back.

Clinton advisers have cited the altered rule, which dates to 1982 and says only that pledged delegates "shall in all good conscience reflect the sentiments of those who elected them."

The same year, The Democratic Party created a new category of delegate -- the so-called "superdelegates" -- party leaders and elected officials who are free to support any candidate they wish, regardless of vote totals in their home states.

Some states require their delegates to support the candidate they are pledged to but most do not.

Earlier this month, Clinton adviser Harold Ickes first raised the prospect that pledged delegates were not legally bound to vote as election results indicate -- an idea that has drawn sharp criticism from supporters of rival Obama. Watch more on the candidates' dust up »

"Despite repeated denials, the Clinton campaign has again admitted that they will go to any length to win," Obama spokesman Bill Burton said again Wednesday.

The Clinton campaign has said that they had not been planning to try to actively convince the Illinois senator's pledged delegates to switch sides and would not do so in the future.

But on a conference call with reporters Tuesday, Ickes defended Clinton's Monday remarks and repeated his view that pledged delegates were free to switch their allegiance at any time.

"I think what Mrs. Clinton was trying to make clear was that no delegate is required by party rules to vote for the candidate for which they're pledged," said Ickes.

"I mean obviously circumstances can change, and people's minds can change about the viability of a particular candidate and that's permitted now under our rules ever since the 1980 convention."

He added that although the rules permitted them to campaign pledged delegates to switch sides, they had not engaged in such an effort.

The timing of the latest round of comments was not an accident, according to veteran Democratic strategist Hank Sheinkopf.

"It keeps them in play. It makes party players understand that they're serious, and they'll stay in the game," Sheinkopf said.

He added that party insiders were likely to view the threat merely as a bargaining chip by an extraordinarily seasoned political team.

Clinton spokesman Phil Singer dismissed the criticism entirely.

"I don't think she floated that idea. I think she was repeating the idea," he told reporters Monday. "Simply stating a fact I don't think is a cause for hysteria."E-mail to a friend